Electric spark gap



1954 E. E. ROBINSON 2,686,887

ELECTRIC SPARK GAP Filed Jan. 8, 1951 Patented Aug. 17, 1954 ELECTRIC SPARK GAP North Wembley, England, mited, London, England Application January 8, 1951, Serial No. 205,000

Eric Ernest Robinson,

assignor to Rotax Li Claims priority, application January 11, 195

1 Claim. 1

This invention relates to electric spark gaps of the three-electrode type, and adapted for use more particularly in engine ignition systems, where a control gap is required to be arranged in series with an ignition gap.

The object of the invention is to provide an improved three-point gap the break-down voltage of which is constant and reliable.

The invention comprises the combination of a pair of main electrodes the adjacent faces of which are substantially flat and parallel with each other, the peripheral configuration of one of them being such as exposes a portion of the face of the other, a needle-like third electrode having one end situated adjacent to the exposed face portion of the one main electrode and sufiiciently far from the other to avoid short-circuiting of the main gap by the third electrode, and an enclosure containing an inert gas at an appropriate pressure.

In the accompanying drawings:

Figure 1 is a sectional plan and Figure 2 is a sectional end View of a spark gap embodying the invention.

Figure 3 is a front elevation and Figure 4 an end view showing one mode of mounting the gap on a supporting base.

Referring to the drawings, there are sealed into opposite ends of a glass or other enclosure a a pair of metal stems b arranged coaxially with each other, and on the adjacent ends of these stems are formed or secured a pair of main electrodes c, d of flat disc-like form made from tungsten or other suitable metal and of about 0.3 inch diameter. The electrode c is made of segmental form so that the circular part of its periphery subtends about 240, and leaves a portion of the face of the other electrode :7. exposed.

Form one side of the enclosure a extends at right angles a branch e through which is inserted the thirdelectrode having a pointed or relatively sharp operative end. This end is located adjacent to the exposed face portion of the electrode d and sufiiciently far from the straight edge of the electrode c to obviate short circuiting of the main gap by discharge across the third electrode instead of between the faces of the main electrodes. In the said branch is also contained a high resistance 9 (conveniently made from carbon) and in contact at one end with the third electrode 1''. The other end of the resistance is connected to a point at substantially the same potential as the stem carrying the segmental electrode 0. The adjacent flat faces of the main electrodes are spaced at any convenient distance Great Britain 0 apart, and the enclosure a is filled with carbon -monoxide or other suitable inert gas at a pressure corresponding to the desired breakdown voltage of the gap between the main electrodes.

The device above described may be mounted on any convenient support, and preferably this includes a pair of flexible or soft pillars made from rubber or like material which at one end are provided with clips for attachment thereto of the outer ends of the main electrode stems.

In the example shown at Figures 3 and 4, there are provided a pair of metal clips it between which are clamped the stems b. At one end each clip is bonded to one end of a rubber block 2. The other end of the rubber block is bonded to a metal piece 7' adapted to be secured to a base It. On the base is secured a spring blade m which bears on the outer end of the resistance g and serves also as a terminal through which the third electrode 1 can be electrically connected to the stem of the electrode 0. Any convenient provision is made for connecting the high tension conductors to the clips h or stems b.

By this invention a gap of the three-electrode type can be provided in a form which ensures the desired reliability of action when in use.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

An electric spark gap of the type specified, comprising in combination a pair of main electrodes having substantially flat faces arranged adjacent to and parallel with each other, and having their peripheries differently shaped so that a portion of one of the said faces is exposed, a needle-like third electrode having one end situated between the planes of the main electrode faces and adjacent to the exposed face portion of the one main electrode and sufficiently far from the other main electrode to avoid short-circuiting of the gap between the main electrode by the third electrode, and a sealed enclosure containing the three electrodes and an inert gas.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,888,068 Brown Nov. 15, 1932 2,438,191 Slack Mar. 23, 1948 2,447,377 Tognola Aug. 17, 1948 2,456,854 Arnott et al Dec. 21, 1948 2,472,115 Mayer June 7, 1949 2,491,979 Hendry Dec. 20, 1949 

